Telephone system



L. H. JOHNSON. TELEiHONE SYSTEM. APPLICATION FILED JAN. 2, 19m.

1 ,36,Q6$, Patented June 10, 1919.

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LEWIS H. JOHNSON, OF BLOOMFIELD, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE SYSTEM.

Specification of Letters Patent. Patented J 11119 10, 19151 Application filed January 2, 1918. Serial No. 209,970.

T 0 all whom it may concern Be it known that I, LEWIS H. JoHNsoN, a citizen of the United States, residing at Bloomfield, in the county of Essex, State of New Jersey, have invented certain new and useful Improvements in Telephone Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems and more particularly to such systems in which connection is to be established between a telephone line terminating at a manual exchange and a telephone line terminating at an automatic exchange.

The principal feature of the invention resides in the provision of means for preventing the false operation of automatic control apparatus at the automatic exchange end of the trunk circuit when connection is made therewith at the manual exchange.

Other features which result from or are incident to the main object above noted will appear during the description of the invention.

One embodiment of this invention is illustrated in the accompanying drawing which shows a telephone line A extending to a manual exchange or central oflice, and there connected in any well-known manner with the cord circuit B. This cord circuit B may be employed to connect the telephone line A with a trunk circuit C extending from the manual exchange to an automatic exchange, where it may connect with an automatic telephone line D terminating at the automatic exchange. The apparatus shown to the left of the dotted line 2, 2 is located at the manual exchange, While that shown to the right thereof is located at the automatic exchange. The apparatus for connecting the trunk circuit C with the automatic line D which is diagrammatically illustrated in the dotted rectangle 3 may be of the type disclosed in the Williams Patent No. 1,237,433. The apparatus shown to the right of the vertical dotted line in Fig. 1 and that shown in Fig.

- 2 of the Williams patent, with the exception of the automatic line may be connected with the three-conductor trunk circuit C shown in the drawing of the present application, in which case the slow-release relay 14 and the rotary and vertical magnets 11 and 23 would Assuming that the subscriber A has initiated a call in the usual manner and that the cord circuit B has been connected therewith, the operator may actuate listening key 6 to connect the operators telephone set therewith. Upon being advised that connection is desired with the line of subscriber D terminating at an automatic exchange, the operator may or may not actuate splitting key 7 The operator then inserts calling plug 8 of the cord circuit B into jack 9 of the trunk circuit C. Relay 10 is thereupon operated over a circuit from battery through resistance 11, contact 12 of relay 13,/the Winding of relay 10, sleeve contacts of the jack 9 and the plug 8, the winding of relay 14, contact 15 of the splitting key 7 and resistance 16 to ground, if the splitting key is not actuated; and if the splitting key is actuated, then through contact 17 of splitting key 7, calling dial 18 and resistance 19 to ground. The resistance 11 is high so that when included in circuit with relay 14, this relay does not attract its armature. The operation of relay 10 causes the lamp 25 assosiated with the jack 9 and the lamp 26 associated with jack 27 of the trunk circuit C to be lighted, the circuit therefor being from battery through the contact of relay 10, normal contact of relay 28, and through the lamps 25 and 26 and resistances 29 and 30 in parallel to ground. These lamps serve as busy signals. Then the splitting key 7 is actuated, relay 35 is energized over a circuit from battery through the winding of relay 35, contact 36 of the listening key 6, and contact 37 of the splitting key 7 to ground. The energization of relay 35 connects impedance coils 38 across the tip and ring conductors of the cord circuit B, so that, upon the complete connection of the plug 8 with the jack 9, relay 4:0 is operated over a circuit from battery through the right-hand winding of relay 40, contact 41 of relay 13, tip contacts of the jack 9 and the plug 8, upper contact of the listening key 6, lower contact of relay 35, impedance coils 38, upper contact of relay 35, middle contact of the listening key 6, ring contacts of the plug 8 and the jack 9 and contact 42 of relay 13 to ground. Relay 40, in operating, causes the energization of a slow release relay 28 over a circuit from battery through the contact of relay 10, contact of relay 40 and the winding of relay 28 to ground. Re-.

lay 28, upon attracting its armatures, sub.-

8 is withdrawn from the jack 9. Relay 13' in operating disconnects the right-hand winding of relay 40 from the tip talking strand of the trunk circuit and removes ground from the ring strand thereof. Relay 13 in operating also closes the normally .open contacts in the talking strands of the trunk circuit C. Contact 12 is opened, removing the high resistance 11 from circuit relation with relay 10, and contact 43 is closed, extending the control conductor 5 through to the automatic exchange where it may pass through the low resistance winding of relay 14 .(see Williams Patent 1237433) and battery to ground. It is pos sible that relay 10 may be released during the short period between the opening of contact 12 and the closure of contact 43, but since relay 28 is made slow to release, relays 40 and 13' will remain energized during this period. Upon the closure of contact 43 relay 10 is then maintained energized, due to battery furnished from the automatic exchange over the control conductor 5. Due to the lower resistance path through the winding of the relay at the automatic exchange established upon the closure of contact 43, relay 14 of the cord circuit B operates, lighting the lamp 44. Upon observing the lighted condition of the lamp 44 the operator may operate the calling dial 18 to select the line of subscriber D. Each time that the contact of the calling dial 18 is opened relay 14 releases its armature so that the lamp 7 44 is intermittently lighted during'the operation ofthe calling dial to furnish a signal to the operator. After the necessary operation of the calling dial to cause the establishment of a connection between the trunk circuit C and the line D, the operator may restore the listening key 6 'and splitting key 7 to normal position, whereupon relay 35 is released. gized over a circuit which includes the resistance 16 and consequently the lamp 44 remains lighted. Should the operator desire to supervise the connection, the actuation of the listening key merely connects the operators telephone set across the talking circuit and has no effect upon the relay 35, since its circuit also includes the normally open contact of the splitting key 7 It will be noted from the above description that by maintaining the control conductor 5 open until after the plug 8 has 1 been completely inserted into the jack 9, it

Relay 14 then remains eneris, impossible through any manipulation of the plug 8 to. cause the false operation of the starting apparatus at the automatic exchange, thereby preventing a false selection.

What is claimed is: V

l. A telephone system comprising a trunk circuit including a normally open control conductor extending from a first to a sec-. ond central office, a telephone line terminating at the second central oflice, switching apparatus thereat controlled over the control conductor from the first central ofice for establishing connection between the I trunk circuit and the telephone line, a link circuit at the first central oiiice, electromag- 3 netic means operated in response to the'connection of the. link circuit with the trunk circuit for closing the normally open controlconductor, and a relay operating upon connection of the link circuit with the trunk circuit and serving to maintain the electromagnetic means in operated condition.

A telephone system comprising a trunk circuit including a normally open control conductor extending from a first to a second central oflice, a telephone line; termiating at the second central ofiice, switching apparatus thereat controlled over the control conductor from the first central ofiice for establishing connection between the trunk circuit and the telephone line, a link circuit at the first central ofiice, a relay operating over portions of the trunk and link circuits upon connection of the link with the trunk circuit, a second relay for closing the normally open control conductor, and an energizin circuit for the second relay established by the closure of'a contact of the first relay.-

3. A telephone system comprising a trunk circuit including a normally open control conductor extending from a first toa second central office,a telephone lineterminating at the second" central oflice, switching apparatus thereat controlledover the control conductor rom the-firstcentraloffice for establishing connection between the trunk circuit and the telephone line, a link circuit at V the first central office, a relay in the control conductor responsive to the connection of the link circuit with the trunk circuit,- a seo- 0nd relay energized over a portion of the talking circuit of the engaged link and'trunk circuits, a' third relay responsive to the energization of the secondrelay to close the normally open control conductor, and a locking circuit for the second relay controlled by thefirst and established simultaneously with the energization of the third relay.

. 4. A telephonesystem comprisinga trunk circuit including a normally open control conductor extending from first to a second central office, a telephone line terminating-at the second central ofiice, switching apparatus thereat controlled over the control conductor from the first central office for establishingconnection between the trunk circuit and the telephone line, a link circuit at the first central office, a relay energized upon connection of the link circuit with the trunk circuit and over a portion of the talking circuit of the engaged link and trunk circuits, a second relay energized upon the energization of the first for closing the normally open control conductor and for disconnecting the first relay from the talking circuit, and a third relay for thereafter maintaining the second relay energized.

5. A telephone system comprising a trunk circuit including a normally open control conductor extending from a first to a second central office, a telephone line terminating at the second central office, switching apparatus thereat controlled over the control conductor from the first central office for establishing connection between the trunk circuit and the telephone line, a link circuit at the first central oflice, a relay in the trunk circuit having two windings and energized through one of its windings upon the connection of the link circuit with the trunk circuit, a second relay energized'upon the energization of the first relay to close the normally open control conductor, and a locking circuit for the first relay including the second winding thereof established simultaneously with the energization of the second relay.

6. A telephone system comprising'a trunk circuit including normally open talking and control conductors extending from a first to a second central ofiice, a telephone line terminating at the second central ofiice, switching apparatus thereat controlled over the control conductor from the first central oflice for establishing connection between the talking conductors of the trunk circuit and the telephone line, a link circuit at the first central oflice, a relay in the trunk circuit responsive to the connection of the link circuit with the trunk circuit, a second relay energized upon the response of the first relay for controlling the closure of the normally open talking and control conductors of the trunk circuit, and a locking circuit for the first relay established. after the energization thereof. 7

7. A telephone system comprising a trunk circuit including normally open talking and control conductors extending from a first to a second central office, a telephone line terminating at a second central office, switching apparatus thereat controlled over the control conductor from the first central office for establishing connection between the talking conductors of the trunk circuit and the telephone line, a link circuit at the first central office, a relay normally connected with one of the talking conductors of the trunk circuit and energized over a portion of that conductor upon the connection of the link circuit'with the trunk circuit, a second relay energized upon the operation oi the first relay to disconnect the first relay from the talking conductor and to close the normally open talking and control conductors, and a locking circuit for the first relay established simultaneously with the energization of the second relay.

8. A telephone system comprising a trunk circuit including a normally open control conductor extending from a first to a second central ofiice, a telephone line terminating at a second gcentral ofiice, switching apparatus thereat controlled over the control conductor from the first central office for establishing connection between the trunk circuit and the telephone line, a telephone line terminating at the first central office, a link circuit thereat connected with the latter telephone line, an operators telephone set at the first central office, a listening key for connecting the telephone set with the link circuit, a splitting key for opening up the talking conductors of the link circuit, an impedance coil, a relay operating upon the actuation of the listening and splitting keys to connect the impedance coil with a talking conductor of the link circuit, a relay in the trunk circuit energized over a path including the impedance coil upon the connection of a link circuit with the trunk circuit, and a second relay energized upon the energization of the first relay of the trunk circuit to close the normally open control conductor.

the control conductor from the first central ofiice for establishing connection between the trunk circuit and the telephone line, a telephone line terminating at the first central oflice, a link circuit thereat connected with the latter telephone line, an operators telephone set at the first central office, a listening key for connecting the telephone set with the link circuit, a splitting key for opening up the talking conductors of the link circuit, an impedance coil, a relay operating upon the actuation of the listening and splitting keys to connect the impedance coil with a talking conductor of the link circuit, a relay in the trunk circuit normally connected with a talking conductor thereof and energized over a circuit including a portion of the talking conductor and the impedance coil upon connection of the link circuit with the trunk circuit, a second relay energized upon the energization of the first trunk relay to disconnect the first relay from the talking conductor and to close the normally open talking and control conductors, and a locking circuit for the first relay established simultaneously with the energization of the second relay.

10. A telephone system comprising a trunk circuit including a talking and a normally open control conductor'extending from a first to a second central office, a telephone line terminating at the second central ofiice, switching apparatus thereat controlled over the control conductor from the first central office for establishing connection between the-trunk circuit and the tele-" conductor extending from a first to a second central ofiice, a telephone line terminating at the second central ofiice, switching apparatus thereat controlled over the control conductor from the first central ofiice for establishing connection between the trunk,

circuit and the telephone line, a link'circuit at the first central ofiice, and a relay operating overportions of the two talking conductors in series upon connection of the link circuit with the trunk circuit for closingthe normally open control conductor.

12: A telephone system comprising a trunk circuit including a normally open Copies of this patent may be obtained forcontrol conductor extending from a first to a second central oflice, a telephone line terminating at the second central office, sWitching apparatus thereat controlled over the control conductor from a, first central oflice for establishing connection betweenthe trunk circuit and the telephone line, a link circuit at the first central ofiice, an operators telephone set, a listening switch for connecting the operators telephone set with the link circuit, and electromagnetic means responsive to the connection of the link circuit with the trunk (circuit when the listening switch is operatedfor closing the normally open control conductor.

13; A telephone system comprising a trunk circuit including a normally open control conductor extending from" a first to a second central oifice, a telephone line ter- I mi'nating at the second central ofiice, switching apparatus thereat controlled over the control conductor from the first central ofiice for establishing connection between the trunk circuit and the telephone line, a link circuit at the first central oifioe, an operators telephone set, a listenin switch for connecting the operators telep ione setwiththe link circuit, a-"relay' inthe trunk circuit controlling the closure of the normally open control conductor, and an energizing circuit for the relay established upon connection of the link circuit with the trunk circuit and including a contact of the listening switch. 1

In Witness whereof, I hereunto subscribe my name this 28th day of December A. D.

LEWIS JOHNSON;

five cents each, by addressing the Commissioner oflatentgx Washington, D. G. 

